Calcium Deficiency Triggers Phloem Remobilization of Cadmium

Cadmium (Cd) is among the most toxic heavy metal to humans. Contamination of Cd in soils poses a serious threat to both crop productivity and human health in many parts of the world. Understanding the molecular mechanisms of Cd transport process will help in developing plants for soil remediation and crop safety. Sedum alfredii is a nonbrassica plant species known to hyperaccumulate Cd. Tian et al. show that low calcium (Ca) supply significantly increased Cd contents in shoots particularly in the young leaves of S. alfredii. This paper also demonstrates that an extremely high Cd signal induced by low Ca supply occurred in the phloem tissues, but not in the xylem tissues. In summary, this paper strongly suggest that Ca deficiency triggers a highly efficient phloem transport system that remobilizes Cd out of its storage sites in plant tissues and subsequently enhances Cd localization in the new growth tissues of S. alfredii. (Summary by Mather Khan) Plant Physiol. 10.1104/pp.16.01348